Fuel Regulator; Fuel Cooler - TOHATSU MFS 25D Service Manual

3) Fuel Regulator

The fuel regulator located inside the vapor separator serves to keep the fuel pressure constant.
The fuel regulator consists of a check valve to actuate the valve/seat, returning the excess fuel b (pressurized) to the
vapor separator when the pressure exceeds a certain value.
Excess fuel is returned to the vapor separator through an internal pipe below the fuel level to prevent it from bubbling.

4) Fuel Cooler

A fuel cooler (heat exchanger) is built into the vapor separator to cool the fuel in the vapor separator, which also uses
the cooling water of the engine. By removing heat from the fuel, this serves to protect from fuel vapor lock and fuel
feed pump (FFP) from wear. Cooling water delivered from the water pump is divided into two passages by the engine
base, one inside the engine and the other to the fuel cooler. Cooling water from the engine base enters from the
cooling water inlet a of the fuel cooler and comes out from the cooling water outlet b before being discharged to the
cooling water check port.
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a High Pressure Fuel from Fuel Feed Pump
b Excessive fuel returns to vapor separator.
a Cooling Water Inlet
b Cooling Water Outlet
b a
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